The heat pipe is a device well-known in the art as a heat transfer mechanism suitable for removal of heat from a predetermined environment or object. Typically, a heat pipe includes a closed evacuated chamber, having inner surfaces lined with a capillary wicking structure saturated with a working fluid. Heat applied to one end or portion of the chamber, called the evaporator section, vaporizes the working fluid contained within the portion of the wick located in the evaporator section. The vaporized fluid transports its absorbed heat of vaporization to a condenser section of the heat pipe and releases it via condensation to a heat sink coupled to that condenser section of the heat pipe. The condensed fluid is drawn back to the evaporator section by the capillary action of the wick, and the vaporing heat transport cycle is repeated. The basic heat pipe concept and a unique method for heat pipe wick fabrication are described in detail in U.S. Pat. No. 3,681,843, entitled HEAT PIPE WICK FABRICATION, issued Aug. 8, 1972, assigned to the assignee of the present invention, and incorporated herein by reference.
While the conventional heat pipe described above operates isothermally at a temperature between that of the heat source and the heat sink, and variations to the basic heat pipe have been employed to establish the operation of the heat pipe at a single preselected temperature, no effective implementation of the basic heat pipe principle for controlling the heat source at various preselected temperatures, controlling the rate of heat flow from the heat source or utilizing heat pipe temperature measurements for determining heat-related parameters, such as fluid flow, have been developed.